Sean Apperson explains the use of the padlock to stifle the double under guard pass in jiu jitsu. This is an awesome counter to a very popular guard pass that can quickly put your opponent in submission danger. The key to the padlock is creating just enough space to slip it on while using your legs and hips to pull the elbow into danger. Be careful not to pull to quickly as you may lose control of the position and lose out on the kimura option.